1. Field of the Invention
The present invention relates generally to seals, and in particular to methods and apparati for sealing at a sliding interface.
2. Description of the Prior Art
In the oil and gas industry, tight seals are frequently required to seal regions which contain extremely corrosive, high temperature, and high pressure fluids, both liquid and gaseous. The sealing task is further complicated by the inaccessibility of the regions to be sealed, which in wellbores are frequently thousands of feet below the earth's surface.
Conventional seals which include rubber components are susceptible to disintegration if continually exposed to the corrosive wellbore fluids. Metal or plastic materials may produce longer lasting seals, but known metal seals such as conventional C-ring and V-ring seals, which are depicted in FIGS. 1a and 1b, are not suitable for use in such hostile environments. Such seals are suitable for use only in rather pristine environments. Furthermore, conventional C-ring and V-ring seals are not able to withstand axial or sliding movement, since such movement would degrade or destroy the seals.
It is one objective of the present invention to provide a seal which operates at a sliding interface of slidably engaged seal members.
It is another objective of the present invention to provide a seal which increases and decreases in sealing engagement in response to changes in pressure of the contained fluid.
It is yet another objective of the present invention to provide a seal which is adapted for use in a wellbore and is composed of a pair of interlocking wellbore tubular members.
It is still another objective of the present invention to provide a sliding interface seal which may be assembled, disassembled, or adjusted by sliding one seal member relative to another seal member under low-pressure differential conditions.
These and other objectives are achieved as is now described. A seal is provided for containing fluid (either gaseous or liquid fluids) under variable pressure in a pressurized region to prevent leakage of the fluid into a less-pressurized region. First and second interfacing seal members are provided and adapted to slidably engage one another at an interface region during makeup of the seal apparatus. A seal region is carried by the first seal member at the interface region and is composed of a deformable material. A seal bead is carried at the interface region by the second seal member and protrudes therefrom. The seal bead is composed of a material harder and less malleable than the seal region, and is adapted for seating in the seal region. At least a portion of the second seal member adjacent the seal bead forms a containment barrier with the pressurized region on one side, and the less-pressurized region on the opposite side. A pressure differential will develop between the pressurized region and the less-pressurized region which urges the seal bead into tighter engagement with the seal region in an amount corresponding to the pressure differential.
In the preferred embodiment, the first and second seal members comprise concentrically interlocking tubular members, and the seal bead is semi-circular in cross-section. Furthermore, in the preferred embodiment, the seal region comprises at least one seal coating disposed on the first seal member at the interface region.
As a method, the present invention includes a number of steps which prevent the passage of pressurized fluid from a pressurized region into a less-pressurized region. First and second interlocking seal members are provided. A deformable seal coating is provided on the first seal member. A protruding seal bead is provided on the second seal member. The first and second interlocking seal members slide together, with the seal bead extending into the deformable layer. The seal bead is forced into tighter contact with the seal coating, in an amount corresponding to the pressure differential between the pressurized region and the less-pressurized region. Therefore, the magnitude of the sealing engagement between the first and second seal members will vary in response to changes in pressure of the pressurized fluid.
The above as well as additional objects, features, and advantages of the invention will become apparent in the following detailed description.